The Uno now uses an ATMega16U2 instead of the ATMega8U2 chip. Faster transfer rates and more memory.
Increased needle socket, convenient you use dupont line.
No drivers needed for Linux or Mac (inf file for Windows is needed and included in the Arduino IDE). The ability to have the Uno show up as a keyboard, mouse, joystick, etc.
Programming: Can be programmed with the Arduino software
Can be used in win 7 and win 8

Technical Details

Size (LWH): 4 inches, 3.7 inches, 0.6 inches
Product Details
Product Dimensions: 4 x 3.7 x 0.6 inches
Shipping Weight: 0.1 pounds (View shipping rates and policies)
ASIN : B00WUC9NZY